The present invention relates to a turntable driving system of a microwave oven, or more specifically to a turntable driving system of low cost and high thermal resistance and having discharge preventive effect.
The conventional turntable driving system of this kind has a construction as shown in FIGS. 6 through 8 for example, in which rotation of the motor shaft (2) of a turntable driving motor (1) is transmitted through a coupling (3) provided on the end of the motor shaft (2) to a turntable roller unit (5) which in turn rotates a turntable (4) supported virtually horizontally by the turntable roller unit (5). As shown in FIG. 5, the turntable roller unit (5) comprises three rollers (8) positioned between the turntable (4) and the inner bottom wall of the oven chamber (7) of the microwave oven body (6), three projections (9) extending radially from the position corresponding to the center bottom of the turntable (4) toward the peripheral edge thereof so as to rotatably support the respective three rollers (8), and a cap (10) concaved downwardly which is provided in the center of the radially extending projections (9) and which is engageable with the coupling (3). The projections (9) and the cap (10) are one integral mold of synthetic resin.
When the above conventional turntable driving system is to be used in a microwave oven with a heater, the projection (9) and the cap (10) of the turntable roller unit (5) must be made of synthetic resin of high thermal resistance because of high temperature in the oven chamber (7) when the oven is operated. However, the thermal resistance of synthetic resin has a limit. Besides, the turntable roller unit (5) using synthetic resin of high thermal resistance incurs high cost.